The effect of anthropogenic aerosols on cloud droplet concentrations and radiative properties is the source of one of the largest uncertainties in the radiative forcing of climate over the industrial ...period. This uncertainty affects our ability to estimate how sensitive the climate is to greenhouse gas emissions. Here we perform a sensitivity analysis on a global model to quantify the uncertainty in cloud radiative forcing over the industrial period caused by uncertainties in aerosol emissions and processes. Our results show that 45 per cent of the variance of aerosol forcing since about 1750 arises from uncertainties in natural emissions of volcanic sulphur dioxide, marine dimethylsulphide, biogenic volatile organic carbon, biomass burning and sea spray. Only 34 per cent of the variance is associated with anthropogenic emissions. The results point to the importance of understanding pristine pre-industrial-like environments, with natural aerosols only, and suggest that improved measurements and evaluation of simulated aerosols in polluted present-day conditions will not necessarily result in commensurate reductions in the uncertainty of forcing estimates.
We derive constraints on energy release, transport and conversion processes in solar flares based on a detailed characterization of the physical parameters of both the thermal plasma and the ...accelerated nonthermal electrons based on X-ray observations. Time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 were obtained using RHESSI hard X-ray observations. This has been supplemented by GOES soft X-ray fluxes. In our companion Paper I, we have used this data set to obtain the basic physical parameters for the thermal plasma. We studied how the thermal energies compare to the energy in nonthermal electrons, and how the various energetics and energy partition depend on flare importance. All flare energetics show a good to excellent correlation with the peak GOES flux. The gravitational energy of the evaporated plasma and the kinetic energy of plasma flows can be neglected in the discussion of flare energetics. Our results support the standard model of solar flares, with the following modifications.
The number of extant species of diatoms is estimated here to be at least 30,000 and probably ca. 100,000, by extrapolation from an eclectic sample of genera and species complexes. Available data, ...although few, indicate that the pseudocryptic species being discovered in many genera are not functionally equivalent. Molecular sequence data show that some diatom species are ubiquitously dispersed. A good case can be made that at least some diatom species and even a few genera are endemics, but many such claims are still weak. The combination of very large species numbers and relatively rapid dispersal in diatoms is inconsistent with some versions of the “ubiquity hypothesis” of protist biogeography, and appears paradoxical. However, population genetic data indicate geographical structure in all the (few) marine and freshwater species that have been examined in detail, sometimes over distances of a few tens of kilometres. The mode of speciation may often be parapatric, in the context of a constantly shifting mosaic of temporarily isolated (meta) populations, but if our “intermediate dispersal hypothesis” is true (that long‐distance dispersal is rare, but not extremely rare), allopatric speciation could also be maximized.
We constrain energy release and particle acceleration processes in solar flares by means of comprehensively characterizing the physical parameters of both the thermal plasma and the accelerated ...nonthermal particles using X-ray data. Our aim is to bridge the gap between detailed case studies and large statistical studies. We obtained time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 using RHESSI hard X-ray observations. These data were used to derive basic physical parameters for the thermal plasma and the injected nonthermal electrons. For the thermal component, this was supplemented by GOES soft X-ray data. Finally, we investigated the relation between thermal and nonthermal parameters. The derived relations between RHESSI- and GOES-derived thermal parameters and the relation between thermal parameters and energy input by nonthermal electrons are consistent with a two-component model of the thermal flare plasma.
• The major obstacle for bioenergy production from switchgrass biomass is the low saccharification efficiency caused by cell wall recalcitrance. Saccharification efficiency is negatively correlated ...with both lignin content and cell wall ester‐linked p‐coumarate: ferulate (p‐CA : FA) ratio. In this study, we cloned and functionally characterized an R2R3‐MYB transcription factor from switchgrass and evaluated its potential for developing lignocellulosic feedstocks. • The switchgrass PvMYB4 cDNAs were cloned and expressed in Escherichia coli, yeast, tobacco and switchgrass for functional characterization. Analyses included determination of phylogenetic relations, in situ hybridization, electrophoretic mobility shift assays to determine binding sites in target promoters, and protoplast transactivation assays to demonstrate domains active on target promoters. • PvMYB4 binds to the AC‐I, AC‐II and AC‐III elements of monolignol pathway genes and down‐regulates these genes in vivo. Ectopic overexpression of PvMYB4 in transgenic switchgrass resulted in reduced lignin content and ester‐linked p‐CA : FA ratio, reduced plant stature, increased tillering and an approx. threefold increase in sugar release efficiency from cell wall residues. • We describe an alternative strategy for reducing recalcitrance in switchgrass by manipulating the expression of a key transcription factor instead of a lignin biosynthetic gene. PvMYB4‐OX transgenic switchgrass lines can be used as potential germplasm for improvement of lignocellulosic feedstocks and provide a platform for further understanding gene regulatory networks underlying switchgrass cell wall recalcitrance.
Summary
Switchgrass (Panicum virgatum L.) has been developed into a dedicated herbaceous bioenergy crop. Biomass yield is a major target trait for genetic improvement of switchgrass. microRNAs have ...emerged as a prominent class of gene regulatory factors that has the potential to improve complex traits such as biomass yield. A miR156b precursor was overexpressed in switchgrass. The effects of miR156 overexpression on SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes were revealed by microarray and quantitative RT‐PCR analyses. Morphological alterations, biomass yield, saccharification efficiency and forage digestibility of the transgenic plants were characterized. miR156 controls apical dominance and floral transition in switchgrass by suppressing its target SPL genes. Relatively low levels of miR156 overexpression were sufficient to increase biomass yield while producing plants with normal flowering time. Moderate levels of miR156 led to improved biomass but the plants were non‐flowering. These two groups of plants produced 58%–101% more biomass yield compared with the control. However, high miR156 levels resulted in severely stunted growth. The degree of morphological alterations of the transgenic switchgrass depends on miR156 level. Compared with floral transition, a lower miR156 level is required to disrupt apical dominance. The improvement in biomass yield was mainly because of the increase in tiller number. Targeted overexpression of miR156 also improved solubilized sugar yield and forage digestibility, and offered an effective approach for transgene containment.
Context. Large-scale wavelike disturbances have been observed in the solar corona in the EUV range since more than a decade. The physical nature of these so-called “EIT waves” is still being debated ...controversially. The two main contenders are on the one hand MHD waves and/or shocks, and on the other hand magnetic reconfiguration in the framework of an expanding CME. There is a lot of observational evidence backing either one or the other scenario, and no single model has been able to reproduce all observational constraints, which are partly even contradictory. This suggests that there may actually exist different classes of coronal waves that are caused by distinct physical processes. Then, the problems in interpreting coronal waves would be mainly caused by mixing together different physical processes. Aims. We search for evidence for physically different classes of large-scale coronal EUV waves. Methods. Kinematics is the most important characteristic of any moving disturbance, hence we focus on this aspect of coronal waves. Identifying distinct event classes requires a large event sample, which is up to now only available from SOHO/EIT. We analyze the kinematics of a sample of 176 EIT waves. In order to check if the results are severely affected by the low cadence of EIT, we complement this with high-cadence data for 17 events from STEREO/EUVI. In particular, we focus on the wave speeds and their evolution. Results. Based on their kinematical behavior, we find evidence for three distinct populations of coronal EUV waves: initially fast waves (v ≥ 320 km s-1) that show pronounced deceleration (class 1 events), waves with moderate (v ≈ 170−320 km s-1) and nearly constant speeds (class 2), and slow waves (v ≤ 130 km s-1) showing a rather erratic behavior (class 3). Conclusions. The kinematical behavior of the fast decelerating disturbances is consistent with nonlinear large-amplitude waves or shocks that propagate faster than the ambient fast-mode speed and subsequently slow down due to decreasing amplitude. The waves with moderate speeds are consistent with linear waves moving at the local fast-mode speed. Thus both populations can be explained in terms of the wave/shock model. The slow perturbations with erratic behavior, on the other hand, are not consistent with this scenario. These disturbances could well be due to magnetic reconfiguration.
The prosurvival protein BCL-2 is frequently overexpressed in estrogen receptor (ER)-positive breast cancer. We have generated ER-positive primary breast tumor xenografts that recapitulate the primary ...tumors and demonstrate that the BH3 mimetic ABT-737 markedly improves tumor response to the antiestrogen tamoxifen. Despite abundant BCL-XL expression, similar efficacy was observed with the BCL-2 selective inhibitor ABT-199, revealing that BCL-2 is a crucial target. Unexpectedly, BH3 mimetics were found to counteract the side effect of tamoxifen-induced endometrial hyperplasia. Moreover, BH3 mimetics synergized with phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitors in eliciting apoptosis. Importantly, these two classes of inhibitor further enhanced tumor response in combination therapy with tamoxifen. Collectively, our findings provide a rationale for the clinical evaluation of BH3 mimetics in therapy for breast cancer.
•BH3 mimetics improve response of breast tumor xenografts to endocrine therapy•The efficacy of the BCL-2-selective inhibitor ABT-199 reveals BCL-2 as a key target•Synergy with PI3K/mTOR inhibitors reveals additional combinatorial therapy options•BCL-2 inhibitors counteract tamoxifen-induced endometrial hyperplasia
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